We thank Prof. J.P. Spatz (Department of Biophysical Chemistry, University of Heidelberg and Department of New Materials and Biosystems, Max Planck Institute for Intelligent Systems, Stuttgart) for his kind support. The financial support from the Max-Planck-Gesellschaft and the Deutsche Forschungsgemeinschaft (DFG SFB/TR79 to E.A.C.-A.) are also greatly acknowledged.

1. Synthesis of 11-Mercaptoundecanoyl-N-hydroxysuccinimide Ester (MU-NHS)
<ol>
	<li>Add dropwise a solution of 500 mg N-hydroxysuccinimide and 30 mg 4-(dimethylamino)pyridine in 10 ml acetone (p.a.) to 1 g 11-mercaptoundecanoic acid in 40 ml dichloromethane (p.a.) at room temperature (RT).</li>
	<li>Cool the reaction to 0 &#176;C and add dropwise 1.1 g N,N&#39;-dicyclohexylcarbodiimide in 10 ml dichloromethane (under nitrogen atmosphere). Keep the reaction at low temperature for 1 hr and then stir at RT overnight.</li>
	<li>Filter the precipitate and dry it under reduced pressure. Purify the product by flash chromatography with petroleum benzene and ethyl acetate (p.a.) in a ratio of 1:1.</li>
</ol>
2. Preparation of Homogeneous Gold Layers
<ol>
	<li>Clean glass coverslips with precision wipes and sonicate them for 5 min in a solution containing a 1:1 mixture of ethyl acetate (p.a.) and methanol (p.a.). Rinse substrates with methanol and dry off under nitrogen flow.</li>
	<li>Place the clean substrates in the sputter coating device. Evacuate the chamber. Remove the uppermost chromium oxide layer from chromium target by sputtering for 60 sec. Place the samples underneath the metal beam and coat them with a 10 nm chromium layer, followed by coating with a 40 nm gold layer.</li>
</ol>
3. Surface Immobilization of BMP-2
<ol>
	<li>Dissolve MU-NHS in N,N-dimethlyformamide (DMF) to a final concentration of approximately 1 mM and incubate gold substrates in the MU-NHS solution at RT for 4 hr under nitrogen atmosphere.</li>
	<li>Sonicate surfaces in DMF for 2 min, rinse with DMF and MeOH and dry off under nitrogen flow.</li>
	<li>Prepare a stock solution of rhBMP-2 in sterile 4 mM HCl with a concentration of 100 &#956;g/ml (store aliquots at -80 &#176;C). For working dilutions (3.5 &#956;g/ml), dilute the stock solution in PBS/NaCl (PBS containing 1 M NaCl) and adjust to pH 8.5 immediately prior to use.</li>
	<li>Incubate surfaces functionalized MU-NHS in the rhBMP-2 working solution at 4 &#176;C overnight. Remove incubation supernatant. Sonicate surfaces in PBS/NaCl for 2 min and wash 3x with sterile PBS/NaCl.</li>
</ol>
4. Surface Characterization
<ol>
	<li>To block unspecific adsorption of antibody, incubate surfaces with a 5% BSA (w/v) in PBS solution for 1 hr at RT, followed by incubation with an anti-BMP-2 antibody (1:100 in 1% (w/v) BSA/PBS solution) for 1 hr at RT. Wash surfaces twice with PBS and sonicate for 30 sec.</li>
	<li>Incubate substrates with HRP-conjugated secondary antibody (1:1,000 in 1% (w/v) BSA/PBS solution) for 30 min at RT, then wash twice with PBS.</li>
	<li>Use Ampliflu Red assay to measure HRP enzymatic activity at 570 nm with a plate reader.</li>
</ol>
5. Analysis of Biological Activity
<ol>
	<li>Seed 1 x 105 mouse C2C12 myoblasts per well in 6-well plates in growth medium, consisting of a high glucose DMEM containing pyruvate supplemented with 10% FBS, 1% penicillin/streptomycin and incubate them for 24 hr at 37 &#176;C/5% CO2.</li>
	<li>Starve cells in serum-free DMEM for 3-5 hr prior to seeding onto the surfaces decorated with immobilized BMP-2.</li>
	<li>For the investigation of short-term signaling induction, replace the medium by 200 &#956;l fresh serum-free DMEM and place the immobilized BMP-2 surfaces above the cells. The surface should be handled with fine tip tweezers to avoid scratching.</li>
	<li>Remove gently surfaces and aspirate the medium with a pipette, wash the cells twice with PBS. Proceed to analysis of cell responses.</li>
	<li>For the analysis of long-term biological activity, plate cells onto surfaces and culture them at 37 &#176;C/5% CO2 in low serum conditions (2% FBS) for six days.</li>
</ol>

<ol>
	<li>Helm, G., Andersson, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Summary+statement:+Bone+morphogenetic+proteins:+Basic+science.">Summary statement: Bone morphogenetic proteins: Basic science.</a> Spine. 27 (16S), S9 (2002).</li><li>Hogan, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+morphogenetic+proteins:+multifunctional+regulators+of+vertebrate+development.">Bone morphogenetic proteins: multifunctional regulators of vertebrate development.</a> Genes Dev. 10 (13), 1580-1594 (1996).</li><li>Reddi, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=BMPs:+from+bone+morphogenetic+proteins+to+body+morphogenetic+proteins.">BMPs: from bone morphogenetic proteins to body morphogenetic proteins.</a> Cytokine Growth Factor Rev. 16, 249-250 (2005).</li><li>Rengachary, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+morphogenetic+proteins:+basic+concepts.">Bone morphogenetic proteins: basic concepts.</a> Neurosurg Focus. 13 (6), 1-6 (2002).</li><li>Schlunegger, M., Gru&#776;tter, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+unusual+feature+revealed+by+the+crystal+structure+at+2.2+&#197;;+resolution+of+human+transforming+growth+factor-&#946;2.">An unusual feature revealed by the crystal structure at 2.2 &#197;; resolution of human transforming growth factor-&#946;2.</a> Nature. 358, 430-434 (1992).</li><li>Scheufler, C., Sebald, W., Hu&#776;lsmeyer, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Crystal+structure+of+human+bone+morphogenetic+protein-2+at+2.7+&#197;+resolution.">Crystal structure of human bone morphogenetic protein-2 at 2.7 &#197; resolution.</a> J. Mol. Biol. 287 (1), 103-115 (1999).</li><li>Nimni, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polypeptide+growth+factors:+targeted+delivery+systems.">Polypeptide growth factors: targeted delivery systems.</a> Biomaterials. 18 (18), 1201-1225 (1997).</li><li>Wozney, J., Rosen, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+morphogenetic+protein+and+bone+morphogenetic+protein+gene+family+in+bone+formation+and+repair.">Bone morphogenetic protein and bone morphogenetic protein gene family in bone formation and repair.</a> Clin. Orthop. Related Res. 346, 26 (1998).</li><li>Rosen, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=BMP+and+BMP+inhibitors+in+bone.">BMP and BMP inhibitors in bone.</a> Annals of the New York Academy of Sciences. 1068, 19-25 (2006).</li><li>Kirsch, T., Sebald, W., Dreyer, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Crystal+structure+of+the+BMP-2-BRIA+ectodomain+complex.">Crystal structure of the BMP-2-BRIA ectodomain complex.</a> Nat. Struct. Biol. 7 (6), 492-496 (2000).</li><li>Keller, S., Nickel, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+recognition+of+BMP-2+and+BMP+receptor+IA.">Molecular recognition of BMP-2 and BMP receptor IA.</a> Nat. Struct. Mol. Biol. 11 (5), 481-488 (2004).</li><li>Miyazono, K., Maeda, S., Imamura, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=BMP+receptor+signaling:+transcriptional+targets,+regulation+of+signals,+and+signaling+cross-talk.">BMP receptor signaling: transcriptional targets, regulation of signals, and signaling cross-talk.</a> Cytokine Growth Factor Rev. 16 (3), 251-263 (2005).</li><li>Nohe, A., Hassel, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+mode+of+bone+morphogenetic+protein+(BMP)+receptor+oligomerization+determines+different+BMP-2+signaling+pathways.">The mode of bone morphogenetic protein (BMP) receptor oligomerization determines different BMP-2 signaling pathways.</a> J. Biol. Chem. 277 (7), 5330-5338 (2002).</li><li>Sieber, C., Kopf, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+BMP+receptor+signaling.">Recent advances in BMP receptor signaling.</a> Cytokine Growth Factor Rev. 20 (5-6), 343-355 (2009).</li><li>Carragee, E. J., Hurwitz, E. L., Weiner, B. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+critical+review+of+recombinant+human+bone+morphogenetic+protein-2+trials+in+spinal+surgery:+emerging+safety+concerns+and+lessons+learned.">A critical review of recombinant human bone morphogenetic protein-2 trials in spinal surgery: emerging safety concerns and lessons learned.</a> Spine J. 11, 471-491 (2011).</li><li>Luginbuehl, V., Meinel, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Localized+delivery+of+growth+factors+for+bone+repair.">Localized delivery of growth factors for bone repair.</a> Eur. J. Pharm. Biopharm. 58 (2), 197-208 (2004).</li><li>Nakaji-Hirabayashi, T., Kato, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oriented+immobilization+of+epidermal+growth+factor+onto+culture+substrates+for+the+selective+expansion+of+neural+stem+cells.">Oriented immobilization of epidermal growth factor onto culture substrates for the selective expansion of neural stem cells.</a> Biomaterials. 28 (24), 3517-3529 (2007).</li><li>Gon&#231;alves, R., Martins, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioactivity+of+immobilized+EGF+on+self-assembled+monolayers:+Optimization+of+the+immobilization+process.">Bioactivity of immobilized EGF on self-assembled monolayers: Optimization of the immobilization process.</a> J. Biomed. Mater. Res. Part A. 94A. 2 (2), 576-585 (2010).</li><li>Pohl, T. L. M., Boergermann, J. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+immobilization+of+bone+morphogenetic+protein+2+via+a+self-assembled+monolayer+formation+induces+cell+differentiation.">Surface immobilization of bone morphogenetic protein 2 via a self-assembled monolayer formation induces cell differentiation.</a> Acta Biomater. 8 (2), 772-780 (2012).</li><li>Love, J., Estroff, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-assembled+monolayers+of+thiolates+on+metals+as+a+form+of+nanotechnology.">Self-assembled monolayers of thiolates on metals as a form of nanotechnology.</a> Chem. Rev. 105 (4), 1103-1169 (2005).</li><li>Katagiri, T., Yamaguchi, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+morphogenetic+protein-2+converts+the+differentiation+pathway+of+C2C12+myoblasts+into+the+osteoblast+lineage.">Bone morphogenetic protein-2 converts the differentiation pathway of C2C12 myoblasts into the osteoblast lineage.</a> J. Cell Biol. 127 (6), 1755-1766 (1994).</li><li>Whitaker, M. J., Quirk, R. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+factor+release+from+tissue+engineering+scaffolds.">Growth factor release from tissue engineering scaffolds.</a> J. Pharm. Pharmacol. 53 (11), 1427-1437 (2001).</li><li>Uludag, H., D'Augusta, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Implantation+of+recombinant+human+bone+morphogenetic+proteins+with+biomaterial+carriers:+a+correlation+between+protein+pharmacokinetics+and+osteoinduction+in+the+rat+ectopic+model.">Implantation of recombinant human bone morphogenetic proteins with biomaterial carriers: a correlation between protein pharmacokinetics and osteoinduction in the rat ectopic model.</a> J. Biomed. Mater. Res. 50 (2), 227-238 (2000).</li><li>Kashiwagi, K., Tsuji, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Directional+BMP-2+for+functionalization+of+titanium+surfaces.">Directional BMP-2 for functionalization of titanium surfaces.</a> Biomaterials. 30 (6), 1166-1175 (2008).</li><li>Karageorgiou, V., Meinel, V. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+morphogenetic+protein-2+decorated+silk+fibroin+films+induce+osteogenic+differentiation+of+human+bone+marrow+stromal+cells.">Bone morphogenetic protein-2 decorated silk fibroin films induce osteogenic differentiation of human bone marrow stromal cells.</a> J. Biomed. Mater. Res. 71 (3), 528-573 (2004).</li><li>Rose, F. R. A. J., Hou, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Delivery+systems+for+bone+growth+factors+-+the+new+players+in+skeletal+regeneration.">Delivery systems for bone growth factors - the new players in skeletal regeneration.</a> J. Pharm. Pharmacol. 56 (4), 415-427 (2004).</li><li>Masters, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Covalent+growth+factor+immobilization+strategies+for+tissue+repair+and+regeneration.">Covalent growth factor immobilization strategies for tissue repair and regeneration.</a> Macromol. Biosci. 11 (9), 1149-1163 (2011).</li><li>Crouzier, T., Fourel, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Presentation+of+BMP-2+from+a+soft+biopolymeric+film+unveils+its+activity+on+cell+adhesion+and+migration.">Presentation of BMP-2 from a soft biopolymeric film unveils its activity on cell adhesion and migration.</a> Adv. Mater. 23 (12), H111-H118 (2011).</li><li>Ruppert, R., Hoffmann, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+bone+morphogenetic+protein+2+contains+a+heparin-binding+site+which+modifies+its+biological+activity.">Human bone morphogenetic protein 2 contains a heparin-binding site which modifies its biological activity.</a> European Journal of Biochemistry. 237 (1), 295-302 (1996).</li><li>Love, J., Estroff, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-assembled+monolayers+of+thiolates+on+metals+as+a+form+of+nanotechnology.">Self-assembled monolayers of thiolates on metals as a form of nanotechnology.</a> Chem. Rev. 105 (4), 1103-1169 (2005).</li><li>Kato, K., Sato, H., Iwata, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immobilization+of+histidine-tagged+recombinant+proteins+onto+micropatterned+surfaces+for+cell-based+functional+assays.">Immobilization of histidine-tagged recombinant proteins onto micropatterned surfaces for cell-based functional assays.</a> Langmuir. 21 (16), 7071-7075 (2005).</li><li>Martins, M., Curtin, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecularly+designed+surfaces+for+blood+deheparinization+using+an+immobilized+heparin-binding+peptide.">Molecularly designed surfaces for blood deheparinization using an immobilized heparin-binding peptide.</a> J. Biomed. Mater. Res. 88 (1), 162-173 (2009).</li><li>Limbut, W., Kanatharana, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+comparative+study+of+capacitive+immunosensors+based+on+self-assembled+monolayers+formed+from+thiourea,+thioctic+acid,+and+3-+mercaptopropionic+acid.">A comparative study of capacitive immunosensors based on self-assembled monolayers formed from thiourea, thioctic acid, and 3- mercaptopropionic acid.</a> Biosens. Bioelectron. 22 (2), 233-240 (2006).</li><li>Patel, N., Davies, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Immobilization+of+protein+molecules+onto+homogeneous+and+mixed+carboxylate-terminated+self-assembled+monolayers.">Immobilization of protein molecules onto homogeneous and mixed carboxylate-terminated self-assembled monolayers.</a> Langmuir. 13 (24), 6485-6490 (1997).</li><li>Hu, J., Duppatla, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Site-specific+PEGylation+of+bone+morphogenetic+protein-2+cysteine+analogues.">Site-specific PEGylation of bone morphogenetic protein-2 cysteine analogues.</a> Bioconjug. Chem. 21 (10), 1762-1772 (2010).</li><li>Hersel, U., Dahmen, C., Kessler, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RGD+modified+polymers:+biomaterials+for+stimulated+cell+adhesion+and+beyond.">RGD modified polymers: biomaterials for stimulated cell adhesion and beyond.</a> Biomaterials. 24 (24), 4385-4415 (2003).</li><li>Cao, T., Wang, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigation+of+spacer+length+effect+on+immobilized+Escherichia+coli+pili-antibody+molecular+recognition+by+AFM.">Investigation of spacer length effect on immobilized Escherichia coli pili-antibody molecular recognition by AFM.</a> Biotechnol. Bioeng. 98 (6), 1109-1122 (2007).</li><li>Puleo, D., Kissling, R., Sheu, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+technique+to+immobilize+bioactive+proteins,+including+bone+morphogenetic+protein-4+(BMP-4),+on+titanium+alloy.">A technique to immobilize bioactive proteins, including bone morphogenetic protein-4 (BMP-4), on titanium alloy.</a> Biomaterials. 23 (9), 2079-2087 (2002).</li></ol>

Authors have nothing to disclose.

In this protocol we describe the preparation of surfaces functionalized with bioactive rhBMP-2. This approach comprises two steps: 1) the initial formation of a self-assembling monolayer (SAM) of a bifunctional linker on the gold surface; 2) covalent immobilization of the rhBMP-2 protein. In previous work, we validated the effective binding of the bifunctional linker and the growth factor, and demonstrated that surface-immobilized rhBMP-2 maintains its biological activity19. The bioactivity of growth factors p...

Bone morphogenetic protein 2 (BMP-2) is a member of the transforming growth factor (TGF-&#946;) family and acts as inducer of de novo bone formation as well as regulator of several tissues during embryonic development and adult homeostasis1-3. Each monomer of the biologically active homodimeric BMP-2 protein contains a &#34;cysteine knot&#34; motif, which is highly conserved in all BMPs4. Six of the seven cysteine residues form intramolecular disulfide bonds that stabilize each monomer, whereas the seventh cysteine is involved in dimerization, forming an intermolecular bond between the two monomers5,6. This highly conserved cysteine knot defines the three-dimensional structure of the BMP-2 protein and determines its unique properties, such as resistance against heat, denaturants and acidic pH7-9. BMP-2 binds to serine/threonine kinase transmembrane receptors, thereby inducing signal transduction10-12. Depending on the mode of receptor oligomerization, different signaling pathways are activated: a Smad-independent signaling cascade leads to alkaline phosphatase induction via p38 signaling, whereas a Smad-dependent pathway activated by receptor phosphorylation results in Smad complex nuclear translocation and activation of transcription of specific target genes, such as the inhibitor of differentiation (Id)12-14.
In bone, BMP-2 induces the differentiation of mesenchymal stem cells into osteoblasts, thus stimulating the healing and de novo formation of bone. Currently, recombinantly expressed BMP-2 is applied clinically to enhance the healing of fractured sites. A common strategy in bone tissue engineering is the use of injectable growth factors, which is less invasive compared to local delivery systems. However, in vivo studies and clinical applications have shown that the short biological half-life, unspecific localization and rapid local clearance of BMP-2 may lead to several local, ectopic and systemic problems15. Hence, to obtain an effective presentation, the entrapment or immobilization of BMP-2 within or onto materials is necessary for its local and sustained delivery at the target site. Sustained delivery can be achieved with non-covalent retention approaches, such as physical entrapment, adsorption or ion complexation16. However, it is known that unspecific adsorption of proteins to surfaces may results in denaturation of the molecules17. For the covalent binding of growth factors, different types of supports have been developed over the last decade. The use of bifunctional linking molecules that target amino or carboxyl groups of the protein for example, is one type of approach that does not necessarily require protein modification to achieve its immobilization. In fact, while protein modification offers the advantage of controlling protein orientation, the introduction of artificial domains, peptide tags and site-specific chains may alter the biological activity of growth factors17. Thus, to circumvent denaturation due to interaction with the supporting material, surfaces can be functionalized beforehand, for example, with a self-assembled monolayer (SAM) of a linking molecule, followed by coupling of the desired factor18. We have used a SAM-based approach to covalently immobilize BMP-2 onto a surface by targeting its free amine residues and have shown that the immobilized protein retains both its short- and long-term biological activity19. This protocol provides a simple and efficient way to deliver BMP-2 to cells for in vitro studies on the mechanisms which occur at the cell membrane and regulate intracellular signaling responsible for osteogenic signaling.

<table border="1">
	<tbody>
		<tr>
			<td>Name of Material/ Equipment</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments/Description</td>
		</tr>
		<tr>
			<td>N-hydroxysuccinimide</td>
			<td>Sigma-Aldrich</td>
			<td>130672</td>
			<td></td>
		</tr>
		<tr>
			<td>4-(dimethylamino)pyridin</td>
			<td>Sigma-Aldrich</td>
			<td>522805</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>AppliChem</td>
			<td>A2282</td>
			<td></td>
		</tr>
		<tr>
			<td>11-mercaptoundecanoic acid</td>
			<td>Sigma-Aldrich</td>
			<td>674427</td>
			<td></td>
		</tr>
		<tr>
			<td>Dichlormethane</td>
			<td>Merck</td>
			<td>106050</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N&#39;-dicyclohexylcarbodiimide</td>
			<td>Sigma-Aldrich</td>
			<td>D80002</td>
			<td></td>
		</tr>
		<tr>
			<td>Petroleum benzene</td>
			<td>Merck</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Glass coverslips</td>
			<td>Carl Roth</td>
			<td>M 875</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethylacetate</td>
			<td>AppliChem</td>
			<td>A3550</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Carl Roth</td>
			<td>4627</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N-dimethylformamide</td>
			<td>Carl Roth</td>
			<td>T921</td>
			<td></td>
		</tr>
		<tr>
			<td>rhBMP-2</td>
			<td>R&#38;D Systems</td>
			<td>355-BM</td>
			<td>Carrier-free; expressed in E.coli</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>PAA</td>
			<td>H15-002</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Carl Roth</td>
			<td>HN00.2</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly(dimethyl siloxane) (PDMS)</td>
			<td>Dow Corning</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sylgard 184 silicone elastomer kit</td>
			<td>Dow Corning</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-rhBMP-2</td>
			<td>Sigma</td>
			<td>B9553</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-mouse IgG-HRP</td>
			<td>Santa Cruz</td>
			<td>sc-2005</td>
			<td>Secondary antibody</td>
		</tr>
		<tr>
			<td>Ampliflu Red assay</td>
			<td>Sigma</td>
			<td>90101</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modified Eagle Medium (DMEM) (1x), liquid</td>
			<td>Gibco</td>
			<td>41966</td>
			<td>High glucose</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum (FBS)</td>
			<td>Sigma</td>
			<td>F7524</td>
			<td>Sterile filtered, cell culture tested</td>
		</tr>
		<tr>
			<td>Pen/Strep</td>
			<td>Gibco</td>
			<td>15140</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin 0.05% (1x) with EDTA 4Na</td>
			<td>Gibco</td>
			<td>25300</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine (0.1 M)</td>
			<td>Riedel-de Ha&#235;n</td>
			<td>33226</td>
			<td></td>
		</tr>
		<tr>
			<td>IGEPAL CA-630 (1%)</td>
			<td>Sigma</td>
			<td>I8896</td>
			<td>Lysis buffer (ALP assay)19</td>
		</tr>
		<tr>
			<td>Magnesium chloride (MgCl2)(1 mM)</td>
			<td>Carl Roth</td>
			<td>HNO3.2</td>
			<td></td>
		</tr>
		<tr>
			<td>Zinc chloride (ZnCl2) (1 mM)</td>
			<td>Carl Roth</td>
			<td>3533.1</td>
			<td></td>
		</tr>
		<tr>
			<td>p-nitrophenylphosphate (pNPP)</td>
			<td>Sigma</td>
			<td>S0942</td>
			<td>Phosphatase substrate</td>
		</tr>
		<tr>
			<td>Anti-mysin heavy chain (MHC)</td>
			<td>Developmental Studies Hybridoma Bank, University of Iowa</td>
			<td>MF20</td>
			<td>Monoclonal antibody</td>
		</tr>
		<tr>
			<td>Alexa Fluor 488 Goat anti-mouse IgG</td>
			<td>Invitrogen</td>
			<td>A11001</td>
			<td></td>
		</tr>
		<tr>
			<td>DAPI</td>
			<td>Sigma</td>
			<td>D9542</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Ultrsonic bath (Sonorex Super RK 102H), Frequency 35 kHz</td>
			<td>BANDELIN electronic GmbH &#38; Co. KG</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MED 020 Sputtercoating system</td>
			<td>BAL-TEC AG</td>
			<td></td>
			<td>Coating conditions 
			Cr: 120 mA, 1.3 x 10-2 mbar, 30 sec 
			Au: 60 mA, 5.0 x 10-2 mbar, 45 sec</td>
		</tr>
		<tr>
			<td>Tecan Infinite M200 Plate reader</td>
			<td>Tecan</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

covalent binding of bmp-2 on surfaces using a self-assembled monolayer approach

Bone morphogenetic protein 2 (BMP-2) is a growth factor embedded in the extracellular matrix of bone tissue. BMP-2 acts as trigger of mesenchymal cell differentiation into osteoblasts, thus stimulating healing and de novo bone formation. The clinical use of recombinant human BMP-2 (rhBMP-2) in conjunction with scaffolds has raised recent controversies, based on the mode of presentation and the amount to be delivered. The protocol presented here provides a simple and efficient way to deliver BMP-2 for in vitro studies on cells. We describe how to form a self-assembled monolayer consisting of a heterobifunctional linker, and show the subsequent binding step to obtain covalent immobilization of rhBMP-2. With this approach it is possible to achieve a sustained presentation of BMP-2 while maintaining the biological activity of the protein. In fact, the surface immobilization of BMP-2 allows targeted investigations by preventing unspecific adsorption, while reducing the amount of growth factor and, most notably, hindering uncontrolled release from the surface. Both short- and long-term signaling events triggered by BMP-2 are taking place when cells are exposed to surfaces presenting covalently immobilized rhBMP-2, making this approach suitable for in vitro studies on cell responses to BMP-2 stimulation.

In our setup, gold was chosen as excipient since it provides a biologically unspecific but chemically tunable system. Furthermore, the application of self-assembling monolayers entails many benefits: SAMs spontaneously adsorb via their "head-groups" on metals and form monolayers with few defects, while their functional end-groups can be further modified. Thus they provide a platform to tailor the properties of the interface in a controlled yet highly adaptable way20.
For the immobil...

Watch this Scientific Journal Video about Covalent Binding of BMP-2 on Surfaces Using a Self-assembled Monolayer Approach at JoVE.com

Covalent Binding of BMP-2 on Surfaces Using a Self-assembled Monolayer Approach

We describe a method for accomplishing efficient immobilization of BMP-2 on surfaces. Our approach is based on the formation of a self-assembled monolayer to achieve the covalent binding of BMP-2 via its free amine residues. This method is a useful tool to study signaling at the cell membrane.

Bone morphogenetic protein 2 (BMP-2) is a growth factor embedded in the extracellular matrix of bone tissue. BMP-2 acts as trigger of mesenchymal cell ...

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Covalent Bonding and Structure

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13.9K Views.  University of Heidelberg. We describe a method for accomplishing efficient immobilization of BMP-2 on surfaces. Our approach is based on the formation of a self-assembled monolayer to achieve the covalent binding of BMP-2 via its free amine residues. This method is a useful tool to study signaling at the cell membrane.

Video: Covalent Binding of BMP-2 on Surfaces Using a Self-assembled Monolayer Approach

Dependence of Laser-induced Breakdown Spectroscopy Results on Pulse Energies and Timing Parameters Using Soil Simulants

The dependence of some LIBS detection capabilities on lower pulse energies (&lt;100 mJ) and timing parameters were examined using synthetic silicate samples. These samples were used as simulants for soil and contained minor and trace elements commonly found in soil at a wide range of concentrations. For this study, over 100 calibration curves were prepared using different pulse energies and timing parameters; detection limits and sensitivities were determined from the calibration curves. Plasma temperatures were also measured using Boltzmann plots for the various energies and the timing parameters tested. The electron density of the plasma was calculated using the full-width half maximum (FWHM) of the hydrogen line at 656.5 nm over the energies tested. Overall, the results indicate that the use of lower pulse energies and non-gated detection do not seriously compromise the analytical results. These results are very relevant to the design of field- and person-portable LIBS instruments.

LIBS detection capabilities on soil simulants were tested using a range of pulse energies and timing parameters. Calibration curves were used to determine detection limits and sensitivities for different parameters. Generally, the results showed that there was not a significant reduction in detection capabilities using lower pulse energies and non-gated detection.

The  dependence of some LIBS detection capabilities on lower pulse energies (&lt;100  mJ) and timing parameters were examined using synthetic silicate ...

Stabilizing Hepatocellular Phenotype Using Optimized Synthetic Surfaces

Currently, one of the major limitations in cell biology is maintaining differentiated cell phenotype. Biological matrices are commonly used for culturing and maintaining primary and pluripotent stem cell derived hepatocytes. While biological matrices are useful, they permit short term culture of hepatocytes, limiting their widespread application. We have attempted to overcome the limitations using a synthetic polymer coating. Polymers represent one of the broadest classes of biomaterials and possess a wide range of mechanical, physical and chemical properties, which can be fine-tuned for purpose. Importantly, such materials can be scaled to quality assured standards and display batch-to-batch consistency. This is essential if cells are to be expanded for high through-put screening in the pharmaceutical testing industry or for cellular based therapy. Polyurethanes (PUs) are one group of materials that have shown promise in cell culture. Our recent progress in optimizing a polyurethane coated surface, for long-term culture of human hepatocytes displaying stable phenotype, is presented and discussed.

This article will focus on developing polymer coated surfaces for long-term, stable culture of stem cell derived human hepatocytes.

Currently, one of the major limitations in cell biology is maintaining differentiated cell phenotype. Biological matrices are commonly used for culturing ...

An Inverse Analysis Approach to the Characterization of Chemical Transport in Paints

The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in understanding contaminant mass transport and the ability to decontaminate materials. If a material is contaminated, over time, the transport of highly toxic chemicals (such as chemical warfare agent species) out of the material can result in vapor exposure or transfer to the skin, which can result in percutaneous exposure to personnel who interact with the material. Due to the high toxicity of chemical warfare agents, the release of trace chemical quantities is of significant concern. Mapping subsurface concentration distribution and transport characteristics of absorbed agents enables exposure hazards to be assessed in untested conditions. Furthermore, these tools can be used to characterize subsurface reaction dynamics to ultimately design improved decontaminants or decontamination procedures. To achieve this goal, an inverse analysis mass transport modeling approach was developed that utilizes time-resolved mass spectroscopy measurements of vapor emission from contaminated paint coatings as the input parameter for calculation of subsurface concentration profiles. Details are provided on sample preparation, including contaminant and material handling, the application of mass spectrometry for the measurement of emitted contaminant vapor, and the implementation of inverse analysis using a physics-based diffusion model to determine transport properties of live chemical warfare agents including distilled mustard (HD) and the nerve agent VX.

In this paper, a procedure for quantifying the mass transport parameters of chemicals in various materials is presented. This process involves employing an inverse-analysis based diffusion model to vapor emission profiles recorded by real-time, mass spectrometry in high vacuum.

The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in ...

Dynamic Electrochemical Measurement of Chloride Ions

This protocol describes the dynamic measurement of chloride ions using the transition time of a silver silver chloride (Ag/AgCl) electrode. Silver silver chloride electrode is used extensively for potentiometric measurement of chloride ions concentration in electrolyte. In this measurement, long-term and continuous monitoring is limited due to the inherent drift and the requirement of a stable reference electrode. We utilized the chronopotentiometric approach to minimize drift and avoid the use of a conventional reference electrode. A galvanostatic pulse is applied to an Ag/AgCl electrode which initiates a faradic reaction depleting the Cl&#713; ions near the electrode surface. The transition time, which is the time to completely deplete the ions near the electrode surface, is a function of the ion concentration, given by the Nernst equation. The square root of the transition time is in linear relation to the chloride ion concentration. Drift of the response over two weeks is negligible (59 &#181;M/day) when measuring 1 mM [Cl&#713;]using a current pulse of 10 Am-2. This is a dynamic measurement where the moment of transition time determines the response and thus is independent of the absolute potential. Any metal wire can be used as a pseudo-reference electrode, making this approach feasible for long-term measurement inside concrete structures.

Dynamic measurement of chloride ions is presented. Transition time of an Ag/AgCl electrode, during a chronopotentiometric technique, can give the concentration of chloride ions in electrolyte. This method does not require a stable conventional reference electrode.

This protocol describes the dynamic measurement of chloride ions using the transition time of a silver silver chloride (Ag/AgCl) electrode. Silver silver ...

Facile Preparation of Internally Self-assembled Lipid Particles Stabilized by Carbon Nanotubes

We present a facile method to prepare nanostructured lipid particles stabilized by carbon nanotubes (CNTs). Single-walled (pristine) and multi-walled (functionalized) CNTs are used as stabilizers to produce Pickering type oil-in-water (O/W) emulsions. Lipids namely, Dimodan U and Phytantriol are used as emulsifiers, which in excess water self-assemble into the bicontinuous cubic Pn3m phase. This highly viscous phase is fragmented into smaller particles using a probe ultrasonicator in presence of conventional surfactant stabilizers or CNTs as done here. Initially, the CNTs (powder form) are dispersed in water followed by further ultrasonication with the molten lipid to form the final emulsion. During this process the CNTs get coated with lipid molecules, which in turn are presumed to surround the lipid droplets to form a particulate emulsion that is stable for months. The average size of CNT-stabilized nanostructured lipid particles is in the submicron range, which compares well with the particles stabilized using conventional surfactants. Small angle X-ray scattering data confirms the retention of the original Pn3m cubic phase in the CNT-stabilized lipid dispersions as compared to the pure lipid phase (bulk state). Blue shift and lowering of the intensities in characteristic G and G&#39; bands of CNTs observed in Raman spectroscopy characterize the interaction between CNT surface and lipid molecules. These results suggest that the interactions between the CNTs and lipids are responsible for their mutual stabilization in aqueous solutions. As the concentrations of CNTs employed for stabilization are very low and lipid molecules are able to functionalize the CNTs, the toxicity of CNTs is expected to be insignificant while their biocompatibility is greatly enhanced. Hence the present approach finds a great potential in various biomedical applications, for instance, for developing hybrid nanocarrier systems for the delivery of multiple functional molecules as in combination therapy or polytherapy.

We report on a smart application of carbon nanotubes for kinetic stabilization of lipid particles that contain self-assembled nanostructures in their cores. The preparation of lipid particles requires rather low concentrations of carbon nanotubes permitting their use in biomedical applications such as drug delivery.

We present a facile method to prepare nanostructured lipid particles stabilized by carbon nanotubes (CNTs). Single-walled (pristine) and multi-walled ...

Highly Stable, Functional Hairy Nanoparticles and Biopolymers from Wood Fibers: Towards Sustainable Nanotechnology

Nanoparticles, as one of the key materials in nanotechnology and nanomedicine, have gained significant importance during the past decade. While metal-based nanoparticles are associated with synthetic and environmental hassles, cellulose introduces a green, sustainable alternative for nanoparticle synthesis. Here, we present the chemical synthesis and separation procedures to produce new classes of hairy nanoparticles (bearing both amorphous and crystalline regions) and biopolymers based on wood fibers. Through periodate oxidation of soft wood pulp, the glucose ring of cellulose is opened at the C2-C3 bond to form 2,3-dialdehyde groups. Further heating of the partially oxidized fibers (e.g., T = 80 &#176;C) results in three products, namely fibrous oxidized cellulose, sterically stabilized nanocrystalline cellulose (SNCC), and dissolved dialdehyde modified cellulose (DAMC), which are well separated by intermittent centrifugation and co-solvent addition. The partially oxidized fibers (without heating) were used as a highly reactive intermediate to react with chlorite for converting almost all aldehyde to carboxyl groups. Co-solvent precipitation and centrifugation resulted in electrosterically stabilized nanocrystalline cellulose (ENCC) and dicarboxylated cellulose (DCC). The aldehyde content of SNCC and consequently surface charge of ENCC (carboxyl content) were precisely controlled by controlling the periodate oxidation reaction time, resulting in highly stable nanoparticles bearing more than 7 mmol functional groups per gram of nanoparticles (e.g., as compared to conventional NCC bearing &#60;&#60; 1 mmol functional group/g). Atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) attested to the rod-like morphology. Conductometric titration, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), dynamic light scattering (DLS), electrokinetic-sonic-amplitude (ESA) and acoustic attenuation spectroscopy shed light on the superior properties of these nanomaterials.

Synthesis schemes to prepare highly stable wood fiber-based hairy nanoparticles and functional cellulose-based biopolymers have been detailed.

Nanoparticles, as one of the key materials in nanotechnology and nanomedicine, have gained significant importance during the past decade. While ...

Microfluidic-based Synthesis of Covalent Organic Frameworks (COFs): A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

Covalent Organic Frameworks (COFs) are a class of porous covalent materials which are frequently synthesized as unprocessable crystalline powders. The first COF was reported in 2005 with much effort centered on the establishment of new synthetic routes for its preparation. To date, most available synthetic methods for COF synthesis are based on bulk mixing under solvothermal conditions. Therefore, there is increasing interest in developing systematic protocols for COF synthesis that provide for fine control over reaction conditions and improve COF processability on surfaces, which is essential for their use in practical applications. Herein, we present a novel microfluidic-based method for COF synthesis where the reaction between two constituent building blocks, 1,3,5-benzenetricarbaldehyde (BTCA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB), takes place under controlled diffusion conditions and at room temperature. Using such an approach yields sponge-like, crystalline fibers of a COF material, hereafter called MF-COF. The mechanical properties of MF-COF and the dynamic nature of the approach allow the continuous production of MF-COF fibers and their direct printing onto surfaces. The general method opens new potential applications requiring advanced printing of 2D or 3D COF structures on flexible or rigid surfaces.

Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

We present a novel microfluidic-based method for synthesis of covalent organic frameworks (COFs). We demonstrate how this approach can be used to produce continuous COF fibers, and also 2D or 3D COF structures on surfaces.

Covalent Organic Frameworks (COFs) are a class of porous covalent materials which are frequently synthesized as unprocessable crystalline powders. The ...

Light-driven Molecular Motors on Surfaces for Single Molecular Imaging

The design and synthesis of a synthetic system that aims for the direct visualization of a synthetic rotary motor at the single molecule level on surfaces are demonstrated. This work requires careful design, considerable synthetic effort, and proper analysis. The rotary motion of the molecular motor in solution is shown by 1H NMR and UV-vis absorption spectroscopy techniques. In addition, the method to graft the motor onto an amine-coated quartz is described. This method helps to gain more insight into molecular machines.

The manuscript describes how to synthesize and graft a molecular motor on surfaces for single molecular imaging.

The design and synthesis of a synthetic system that aims for the direct visualization of a synthetic rotary motor at the single molecule level on surfaces ...

Ion Mobility-Mass Spectrometry Techniques for Determining the Structure and Mechanisms of Metal Ion Recognition and Redox Activity of Metal Binding Oligopeptides

Electrospray ionization (ESI) can transfer an aqueous-phase peptide or peptide complex to the gas-phase while conserving its mass, overall charge, metal-binding interactions, and conformational shape. Coupling ESI with ion mobility-mass spectrometry (IM-MS) provides an instrumental technique that allows for simultaneous measurement of a peptide&#8217;s mass-to-charge (m/z) and collision cross section (CCS) that relate to its stoichiometry, protonation state, and conformational shape. The overall charge of a peptide complex is controlled by the protonation of 1) the peptide&#8217;s acidic and basic sites and 2) the oxidation state of the metal ion(s). Therefore, the overall charge state of a complex is a function of the pH of the solution that affects the peptides metal ion binding affinity. For ESI-IM-MS analyses, peptide and metal ions solutions are prepared from aqueous-only solutions, with the pH adjusted with dilute aqueous acetic acid or ammonium hydroxide. This allows for pH dependence and metal ion selectivity to be determined for a specific peptide. Furthermore, the m/z and CCS of a peptide complex can be used with B3LYP/LanL2DZ molecular modeling to discern binding sites of the metal ion coordination and tertiary structure of the complex. The results show how ESI-IM-MS can characterize the selective chelating performance of a set of alternative methanobactin peptides and compare them to the copper-binding peptide methanobactin.

Ion mobility-mass spectrometry and molecular modeling techniques can characterize the selective metal chelating performance of designed metal-binding peptides and the copper-binding peptide methanobactin. Developing new classes of metal chelating peptides will help lead to therapeutics for diseases associated with metal ion misbalance.

Electrospray ionization (ESI) can transfer an aqueous-phase peptide or peptide complex to the gas-phase while conserving its mass, overall charge, ...

Synthesis of Information-bearing Peptoids and their Sequence-directed Dynamic Covalent Self-assembly

This protocol presents the use of Lewis acidic multi-role reagents to circumvent kinetic trapping observed during the self-assembly of information-encoded oligomeric strands mediated by paired dynamic covalent interactions in a manner mimicking the thermal cycling commonly employed for the self-assembly of complementary nucleic acid sequences. Primary amine monomers bearing aldehyde and amine pendant moieties are functionalized with orthogonal protecting groups for use as dynamic covalent reactant pairs. Using a modified automated peptide synthesizer, the primary amine monomers are encoded into oligo(peptoid) strands through solid-phase submonomer synthesis. Upon purification by high-performance liquid chromatography (HPLC) and characterization by electrospray ionization mass spectrometry (ESI-MS), sequence-specific oligomers are subjected to high-loading of a Lewis acidic rare-earth metal triflate which both deprotects the aldehyde moieties and affects the reactant pair equilibrium such that strands completely dissociate. Subsequently, a fraction of the Lewis acid is extracted, enabling annealing of complementary sequence-specific strands to form information-encoded molecular ladders characterized by matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS). The simple procedure outlined in this report circumvents kinetic traps commonly experienced in the field of dynamic covalent assembly and serves as a platform for the future design of robust, complex architectures.

A protocol is presented for the synthesis of information-encoded peptoid oligomers and for the sequence-directed self-assembly of these peptoids into molecular ladders using amines and aldehydes as dynamic covalent reactant pairs and Lewis acidic rare-earth metal triflates as multi-role reagents.

This protocol presents the use of Lewis acidic multi-role reagents to circumvent kinetic trapping observed during the self-assembly of information-encoded ...